In-situ anion exchange synthesis of AgBr/Ag2CO3 hybrids with enhanced visible light photocatalytic activity and improved stability

Nanotechnologies for environmental remediation and their ecotoxicological impacts

Environmental nanoremediation is an emerging technology that aims to rapidly and efficiently remove contaminants from the polluted sites using engineered nanomaterials (ENMs). Inorganic nanoparticles which are generally metallic, silica-based, carbon-based, or polymeric in nature serve to remediate through chemical reactions, filtration, or adsorption. Their greater surface area per unit mass and high reactivity enable them to treat groundwater, wastewater, oilfields, and toxic industrial contaminants. Despite the growing interest in nanotechnological solutions for bioremediation, the environmental and human hazard associated with their use is raising concerns globally. Nanoremediation techniques when compared to conventional remediation solutions show increased effectivity in terms of cost and time; however, the main challenge is the ability of ENMs to remove contaminants from different environmental mediums by safeguarding the ecosystem. ENMs improving the accretion of the pollutant and increasing their bioavailability should be rectified along with the vigilant management of their transfer to the upper levels of the food chain which subsequently causes biomagnification. The ecosystem-centered approach will help monitor the ecotoxicological impacts of nanoremediation considering the safety, sustainability, and proper disposal of ENMs. The environment and human health risk assessment of each novel engineered nanomaterial along with the regulation of life cycle assessment (LCA) tools of ENMs for nanoremediation can help investigate the possible environmental hazard. This review focuses on the currently available nanotechnological methods used for environmental remediation and their potential toxicological impacts on the ecosystem.

WO3/Ag2CO3 Mixed Photocatalyst with Enhanced Photocatalytic Activity for Organic Dye Degradation

The development of an efficient photocatalyst with superior activity under visible light has been regarded as a significant strategy for pollutant degradation and environmental remediation. Herein, a series of WO₃/Ag₂CO₃ mixed photocatalysts with different proportions were prepared by a simple mixing method and characterized by XRD, SEM, TEM, XPS, and DRS techniques. The photocatalytic performance of the WO₃/Ag₂CO₃ mixed photocatalyst was investigated by the degradation of rhodamine B (RhB) under visible light irradiation (λ > 400 nm). The photocatalytic efficiency of the mixed WO₃/Ag₂CO₃ photocatalyst was rapidly increased with the proportion of Ag₂CO₃ up to 5%. The degradation percentage of RhB by WO₃/Ag₂CO₃-5% reached 99.7% within 8 min. The pseudo-first-order reaction rate constant of WO₃/Ag₂CO₃-5% (0.9591 min^-1) was 118- and 14-fold higher than those of WO₃ (0.0081 min^-1) and Ag₂CO₃ (0.0663 min^-1). The catalytic activities of the mixed photocatalysts are not only higher than those of the WO₃ and Ag₂CO₃ but also higher than that of the WO₃/Ag₂CO₃ composite prepared by the precipitation method. The activity enhancement may be because of the easier separation of photogenerated electron-hole pairs. The photocatalytic mechanism was investigated by free radical capture performance and fluorescence measurement. It was found that light-induced holes (h⁺) was the major active species and superoxide radicals (·O₂ ^-) also played a certain role in photocatalytic degradation of RhB.

Visible light-conducting polymer nanocomposites as efficient photocatalysts for the treatment of organic pollutants in wastewater

This review compiles recent advances and challenges on photocatalytic treatment of wastewater using nanoparticles, nanocomposites, and polymer nanocomposites as photocatalyst. The review provides an overview of the fundamental principles of photocatalytic treatment along the recent advances on photocatalytic treatment, especially on the modification strategies and operational conditions to enhance treatment efficiency and removal of recalcitrant organic contaminants. The different types of photocatalysts along the key factors influencing their performance are also critically discussed and recommendations for future research are provided.

Nanoremediation technologies for sustainable remediation of contaminated environments: Recent advances and challenges

A major and growing concern within society is the lack of innovative and effective solutions to mitigate the challenge of environmental pollution. Uncontrolled release of pollutants into the environment as a result of urbanisation and industrialisation is a staggering problem of global concern. Although, the eco-toxicity of nanotechnology is still an issue of debate, however, nanoremediation is a promising emerging technology to tackle environmental contamination, especially dealing with recalcitrant contaminants. Nanoremediation represents an innovative approach for safe and sustainable remediation of persistent organic compounds such as pesticides, chlorinated solvents, brominated or halogenated chemicals, perfluoroalkyl and polyfluoroalkyl substances (PFAS), and heavy metals. This comprehensive review article provides a critical outlook on the recent advances and future perspectives of nanoremediation technologies such as photocatalysis, nano-sensing etc., applied for environmental decontamination. Moreover, sustainability assessment of nanoremediation technologies was taken into consideration for tackling legacy contamination with special focus on health and environmental impacts. The review further outlines the ecological implications of nanotechnology and provides consensus recommendations on the use of nanotechnology for a better present and sustainable future.

Facile fabrication of highly catalytic-active Ag2CO3/AgBr/graphene oxide ternary composites towards the photocatalytic wastewater treatment

Ag₂CO₃/AgBr/graphene oxide (Ag₂CO₃/AgBr/GO) ternary composites with different percentages of GO were fabricated by a facile co-precipitation strategy. The composites were characterized in the aspect of phase composition, light absorption performance, and micromorphology etc. The activity of the composites was studied by photocatalytic degradation of colored organic dye (rhodamine B, RhB) and colorless organics (phenol) under the shine of visible light. The optimized Ag₂CO₃/AgBr/GO-7.5 composites revealed the most excellent photocatalytic activity, which exhibited an apparent reaction rate constant exceeding that of pristine AgBr and Ag₂CO₃ by a factor of 107 and 5.63, respectively. The outstanding performance can be attributed to the effective separation of electrons and holes as well as the strong light absorption ability resulting from the Ag₂CO₃/AgBr/GO heterostructure. Moreover, it was verified that h⁺ and •O₂^- were two major active substances responsible for the decomposition of organic pollutants according to the free radical-trapping experiments. Besides, a probable reaction mechanism referring to the charge transfer and separation in the composites was proposed and discussed in detail.

Synthesis of LaFeO3/Ag2CO3 Nanocomposites for Photocatalytic Degradation of Rhodamine B and p-Chlorophenol under Natural Sunlight

Novel LaFeO₃/Ag₂CO₃ nanocomposites are synthesized by co-precipitation method for photocatalytic degradation of Rhodamine B (RhB) and p-chlorophenol under visible light irradiation. Heterostructures between LaFeO₃ and Ag₂CO₃ semiconductors are formed during the synthesis of these nanocomposites. Among the nanocomposites prepared with different ratios of LaFeO₃ and Ag₂CO₃, 1% LaFeO₃/Ag₂CO₃ shows the highest photocatalytic activity for the degradation of RhB. Maximum electron-hole pair decoupling efficiency is observed in 1% LaFeO₃/Ag₂CO₃, which causes the greater activity of the heterostructure. Degradation efficiency of 99.5% for RhB and 59% for p-chlorophenol has been obtained under natural sunlight within 45 min. Interestingly, the stability of Ag₂CO₃ is improved dramatically after making nanocomposite, and no decomposition of the catalyst was observed even after several photocatalytic cycles. Reactive oxygen species scavenging experiments with p-benzoquinone, isopropyl alcohol, and ammonium oxalate suggest that a major degradation process is caused by holes. Degradation of RhB into small organic moieties is detected using LC-MS technique. Further, the efficient mineralization of the degradation products occurs during the catalytic process.

Zinc oxide-decorated polypyrrole/chitosan bionanocomposites with enhanced photocatalytic, antibacterial and anticancer performance

A bio-nanocomposite matrix of polypyrrole grafted ZnO/chitosan (Ppy/C/Z) was synthesized via the in situ polymerization of pyrrole with different weight fractions of ZnO. Incorporation of ZnO nanoparticles with polypyrrole enhances the photocatalytic, antibacterial as well as cytotoxic properties of the resultant composite. Characterizations of the synthesized product were performed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermal analysis (TGA and DTA). Surface morphology and particle size were determined by SEM and TEM. The elemental composition of the material was studied by EDX coupled with SEM. Electrochemical surface area was calculated from electrochemical double layer capacitance (EDLC) measurements using cyclic voltammetry. The photocatalytic activity of the composite material was tested by monitoring the degradation of reactive orange-16 (RO-16), Coomassie Brilliant Blue R-250 (CBB-R-250) and Methylene Blue (MB) dyes and the composite was found to be an effective catalyst in the presence of a UV light source. Various scavengers were used to detect the reactive species involved in the photocatalytic process. Furthermore, the stability of the photocatalyst was assessed by recycling experiments. Moreover, the Ppy/C/Z bio-nanocomposite shows potential application with anti-bacterial and anti-cancer activity against Gram-positive and Gram-negative bacterial pathogens and human cancer cell lines (HeLa and MCF-7). The experimental data confirm that the bio-nanocomposite of Ppy/C/Z showed excellent anti-bacterial and anti-cancer activity as compared to a pristine polypyrrole and chitosan formulation (Ppy/C). The apoptosis data with varying concentrations of Ppy/C/Z reveal the remarkable activity against these cancer cell lines.

Bio-nanocomposites were synthesized via grafting polypyrrole/ZnO onto chitosan chain for the photodegradation of organic pollutants and biomedical applications.

Fabrication of Ag/AgBr/Ag3VO4 composites with high visible light photocatalytic performance

Herein, Ag/AgBr/Ag₃VO₄ composites were synthesized by a simple continuous precipitation method. The obtained composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL). Photocatalytic performance of the composites was assessed by the degradation of methyl orange (MO) and tetracycline hydrochloride (TC) under visible light, and the effects of different nominal mass ratios of AgBr and Ag₃VO₄ on the photocatalytic activity were investigated. The results showed that after 20 min of visible light irradiation (λ > 420 nm), the removal rate of MO in the presence of a 5 : 1 sample reached 98.6%. The EIS and photocurrent results demonstrated that the enhancement of the visible light photocatalytic activity was attributed to the efficient electron–hole pair separation. In addition, the scavenging reactions conducted via the addition of different scavengers confirmed that h⁺ and ·O²⁻ were the main active species in the reaction. The present study offers potential for the degradation of contaminants.

Ag/AgBr/Ag₃VO₄ composites were synthesized by a simple continuous precipitation method, which were used to degrade organic pollutants and found to have excellent photocatalytic properties.

Double Effect Electron Transfer System in the AgBr/ZnO Composite with Enhanced Photocatalytic Degradation Performance against 3-Chlorophenol under Visible Light Irradiation

Visible light-driven novel and highly efficient AgBr/ZnO photocatalysts were synthesized by a facile precipitation and dehydration methods. The synthesized samples were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Visible diffuse reflectance spectroscopy (UV-Vis DRS), and photoluminescence (PL) techniques. Within various combinations of AgBr and ZnO components in the composites, 1AgBr/ZnO showed higher photocatalytic activity against 3-chlorophenol (3-CP). UV-Vis DRS spectra showed that the absorbance of AgBr/ZnO was higher than pure ZnO in the visible light region. The PL results showed that efficient inhibition of the generated electron/hole pairs has occurred during the degradation process due to the formation of heterojunctions. The forming of metallic Ag⁰ by photogenerated electrons, which captures Ag⁺ ions, could act as an interfacial charge transmission bridge in the AgBr/ZnO composite. These results provided an important insight into the plasmonic Ag particles to obtain an efficient visible light-driven photocatalyst. In addition, the possible mechanism of charge transfers and separation of electron/hole pairs were also evaluated in detail.

Sono-precipitation of Ag2CrO4-C composite enhanced by carbon-based materials (AC, GO, CNT and C3N4) and its activity in photocatalytic degradation of acid orange 7 in water

Enhancing the photocatalytic activity of Ag₂CrO₄ with coupled carbon-based materials like activated carbon, graphene oxide, carbon nanotubes and carbon nitride has been investigated in removal of Acid Orange 7 from wastewater. Sono precipitated Ag₂CrO₄-C composite based photocatalysts were characterized by XRD, BET, FESEM, FTIR and UV-vis DRS and the photocatalytic activity of theses samples was evaluated in terms of degradation amount of acid orange 7 under visible light irradiations. BET analysis showed that with addition of carbon based materials, the specific surface area of the Ag₂CrO₄-C composite increased. XRD analysis indicated that the crystallinity of Ag₂CrO₄ peaks decreased after addition of all studied carbon-based materials and C₃N₄ has lowered the crystallinity of Ag₂CrO₄ less than others. Higher crystallinity has the positive effect of higher photocatalytic activity because among above mentioned composites, Ag₂CrO₄-C₃N₄ photocatalyst exhibited higher photocatalytic activity and stability under visible light irradiations. DRS analysis confirmed good match of electronic structures of Ag₂CrO₄ and C₃N₄. On the other hand Ag₂CrO₄ and C₃N₄ formed heterojunction which separates photo-generated electron-hole pairs effectively. Also evaluation of photocatalytic reaction in various operating parameters showed Ag₂CrO₄-C₃N₄ had the highest photocatalytic activity in neutral pH and 1g/L of catalyst loading.

Novel visible light-driven Cu-based MOFs/Ag2O composite photocatalysts with enhanced photocatalytic activity toward the degradation of orange G: their photocatalytic mechanism and optimization study

The present work is devoted to the synthesis of two visible light-driven Cu-based metal organic frameworks composited with Ag₂O nanoparticles.

In-situ synthesis of amorphous silver silicate/carbonate composites for selective visible-light photocatalytic decomposition

Coupling two different semiconductors to form composite photocatalysts is an extremely significant technique for environmental remediation. Here, a one-step in-situ precipitation method has been developed to prepare amorphous silver silicate/carbonate (AgSiO/Ag₂CO₃) nanoparticles (NPs) composites, which are well dispersed sphere-like particles with the sizes of around ~50–100 nm. The high-efficiency photocatalytic activities under visible light (VL) have been carefully evaluated, and the AgSiO/Ag₂CO₃ NPs composites exhibit selective photocatalytic degradations on Methylene Blue (MB) and Rhodamine B (RhB). The maximum degradation rate for MB can reach ~99.1% within ~40 min under VL irradiation, much higher than that of RhB (~12%) in the same condition, which can be ascribed to (I) the smaller molecule size of MB than that of RhB, (II) the fast charge separation between AgSiO NPs and Ag₂CO₃ NPs, abundant heterojunction interfaces as well as fully exposed reactive sites. These composites are proposed to be an example for the preparation of other silicate composite photocatalysts for practical applications in environmental remediation.

Decoration of TiO2/g-C3N4 Z-scheme by carbon dots as a novel photocatalyst with improved visible-light photocatalytic performance for the degradation of enrofloxacin

A novel visible-light-driven CDs/TiO₂/g-C₃N₄ photocatalyst was successfully synthesized by doping CDs in TiO₂ nanoparticles and the surface of g-C₃N₄ nanosheets via a facile hydrothermal process and was confirmed by characterization methods.

Synthesis and characterization of Z-scheme In2S3/Ag2CrO4 composites with an enhanced visible-light photocatalytic performance

Efficient charge transfer at the interfaces of an In₂S₃/Ag₂CrO₄ composite, due to the formation of a Z-scheme system between In₂S₃ and Ag₂CrO₄, effectively facilitates photogenerated electron–hole pair separation.

Novel bio-nanocomposite materials for enhanced biodegradability and photocatalytic activity

Novel bio-nanocomposites with enhanced biodegradability and photocatalytic activity were prepared by chemical in situ polymerization.

Facile synthesis of ternary Ag/AgBr-Ag(2)CO(3) hybrids with enhanced photocatalytic removal of elemental mercury driven by visible light

A novel technique for photocatalytic removal of elemental mercury (Hg(0)) using visible-light-driven Ag/AgBr-Ag2CO3 hybrids was proposed. The ternary Ag/AgBr-Ag2CO3 hybrids were synthesized by a simple modified co-precipitation method and characterized by N2 adsorption-desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), UV-vis diffused reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) techniques. The effects of AgBr content, fluorescent lamp (FSL) irradiation, solution temperature, SO2 and NO on Hg(0) removal were investigated in detail. Furthermore, a possible reaction mechanism for higher Hg(0) removal was proposed, and the simultaneous removal of Hg(0), SO2 and NO was studied. The results showed that a high efficiency of Hg(0) removal was obtained by using Ag/AgBr-Ag2CO3 hybrids under fluorescent lamp irradiation. The AgBr content, FSL irradiation, solution temperature, and SO2 all exhibited significant effects on Hg(0) removal, while NO had slight effect on Hg(0) removal. The addition of Ca(OH)2 demonstrated a little impact on Hg(0) removal and could significantly improve the SO2-resistance performance of Ag/AgBr(0.7)-Ag2CO3 hybrid. The characterization results exhibited that hydroxyl radical (OH), superoxide radical (O2(-)), hole (h(+)), and Br(0), were reactive species responsible for removing Hg(0), and the h(+) played a key role in Hg(0) removal.

Facile fabrication and enhanced visible-light photocatalytic activity of In2O3/Ag2CrO4 composites

The efficient charge transfer at the interfaces of In₂O₃/Ag₂CrO₄ composite due to the formation of Z-scheme system composed of In₂O₃, Ag and Ag₂CrO₄, which effectively improved the separation and transfer of photogenerated charge carriers.

Universal degradation performance of a high-efficiency AgBr/Ag2CO3 photocatalyst under visible light and an insight into the reaction mechanism

A AgBr/Ag₂CO₃ photocatalyst exhibited excellent photocatalytic activity and stability under visible light and a two-stage photocatalytic mechanism was proposed.

Efficient visible light photocatalytic activity and enhanced stability of BiOBr/Cd(OH)2 heterostructures

The BiOBr/Cd(OH)₂ heterojunction formation decreased the charge recombination phenomenally and imparted significant visible light response.

Fabrication and characterization of Ag2CO3/SnS2 composites with enhanced visible-light photocatalytic activity for the degradation of organic pollutants

The efficient charge transfer at the interfaces of the Ag₂CO₃/SnS₂ composite due to the inner established electric field (E), which effectively facilitated interfacial charge transfer and improved photogenerated electron–hole pairs separation.

Ag2S sensitized mesoporous Bi2WO6 architectures with enhanced visible light photocatalytic activity and recycling properties

To harvest solar energy more efficiently, novel Ag₂S/Bi₂WO₆ heterojunctions were synthesized by a hydrothermal route.